The present invention relates to horology and more particularly to the frequency adjustment of an electronic watch.
In recent years great interest has been shown in using piezoelectric crystal oscillators as highly accurate time bases in horological instruments.
However, it is difficult and, therefore, expensive to produce a small piezoelectric crystal having an exact predetermined frequency. For example, an error of only 0.01% (one part in ten thousand) in the frequency results in an error of about 10 seconds a day or 5 minutes a month, which is unacceptable. This difficulty increases when the problems of mass production are considered. Highly trained workers are required to produce suitable crystals because of the small size of the crystal and the need for its exact frequency. And even when the crystal is accurately manufactured to its specified frequency, it may drift from that frequency due to the effects of age and environmental conditions. Generally, the watch repairman would not have the tools or the skill to readjust the frequency of the piezoelectric crystal.
A partial list of prior art patents of interest includes U.S. Pat. No. 3,540,207 to Keeler, U.S. Pat. No. 3,756,014 to Zatsky et al, U.S. Pat. No. 3,777,471 to Koehler et al, U.S. Pat. No. 3,914,706 to Hammer et al and U.S. Pat. No. 3,916,612 to Shigeru Morokawa et al. These prior art patents are merely typical of the art and are not in any way intended to be an all-inclusive list of pertinent prior art.
Therefore, it is an objective of the present invention to provide a system in an electronic watch in which the effective frequency of a piezo-electric crystal may be accurately adjusted to an exact predetermined frequency by activation of a plurality of switches.
It is a further objective of the present invention to provide a means for reversible and stepwise adjustment of the effective frequency of the piezoelectric crystal over a wide range of frequencies.
It is a further objective of the present invention to provide a means for reversible and stepwise adjustment of an electronic timepiece to run faster or slower to obtain accurate timekeeping by actuation of a plurality of switches.
It is a further objective of the present invention to provide a new and improved switch and circuit arrangement for adjusting the "effective frequency of the oscillator" over a wide range of frequencies.
It is a still further objective of the present invention to provide a new and improved switch and circuit arrangement for adjusting the output frequency of a count-down circuit.